It is shown that a “nanofluid” consisting of copper nanometer-sized particles dispersed in ethylene glycol has a much higher effective thermal conductivity than either pure ethylene glycol or ethylene glycol containing the same volume fraction of dispersed oxide nanoparticles. The effective thermal conductivity of ethylene glycol is shown to be increased by up to 40% for a nanofluid consisting of ethylene glycol containing approximately 0.3 vol % Cu nanoparticles of mean diameter <10 nm. The results are anomalous based on previous theoretical calculations that had predicted a strong effect of particle shape on effective nanofluid thermal conductivity, but no effect of either particle size or particle thermal conductivity.

Anomalously increased effective thermal conductivities of ethylene glycol-based nanofluids containing copper nanoparticles

Oxide nanofluids were produced and their thermal conductivities were measured by a transient hot-wire method. The experimental results show that these nanofluids, containing a small amount of nanoparticles, have substantially higher thermal conductivities than the same liquids without nanoparticles. Comparisons between experiments and the Hamilton and Crosser model show that the model can predict the thermal conductivity of nanofluids containing large agglomerated Al{sub 2}O{sub 3} particles. However, the model appears to be inadequate for nanofluids containing CuO particles. This suggests that not only particle shape but size is considered to be dominant in enhancing the thermal conductivity of nanofluids.

Measuring Thermal Conductivity of Fluids Containing Oxide Nanoparticles

We have produced nanotube-in-oil suspensions and measured their effective thermal conductivity. The measured thermal conductivity is anomalously greater than theoretical predictions and is nonlinear with nanotube loadings. The anomalous phenomena show the fundamental limits of conventional heat conduction models for solid/liquid suspensions. We have suggested physical concepts for understanding the anomalous thermal behavior of nanotube suspensions. In comparison with other nanostructured materials dispersed in fluids, the nanotubes provide the highest thermal conductivity enhancement, opening the door to a wide range of nanotube applications.

Anomalous thermal conductivity enhancement in nanotube suspensions

Heat transfer characteristics of nanofluids: a review

Pore fluids strongly influence the seismic properties of rocks. The densities, bulk moduli, velocities, and viscosities of common pore fluids are usually oversimplified in geophysics. We use a combination of thermodynamic relationships, empirical trends, and new and published data to examine the effects of pressure, temperature, and composition on these important seismic properties of hydrocarbon gases and oils and of brines. Estimates of in-situ conditions and pore fluid composition yield more accurate values of these fluid properties than are typically assumed. Simplified expressions are developed to facilitate the use of realistic fluid properties in rock models. Pore fluids have properties that vary substantially, but systematically, with composition, pressure, and temperature. Gas and oil density and modulus, as well as oil viscosity, increase with molecular weight and pressure, and decrease with temperature. Gas viscosity has a similar behavior, except at higher temperatures and lower pressures, where the viscosity will increase slightly with increasing temperature. Large amounts of gas can go into solution in lighter oils and substantially lower the modulus and viscosity. Brine modulus, density, and viscosities increase with increasing salt content and pressure. Brine is peculiar because the modulus reaches a maximum at a temperature from 40 to 80°C. Far less gas can be absorbed by brines than by light oils. As a result, gas in solution in oils can drive their modulus so far below that of brines that seismic reflection bright spots may develop from the interface between oil saturated and brine saturated rocks.

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Seismic properties of pore fluids

Diffusion Coefficient of Seven Binary Gaseous Mixtures

On the correlation of experimental viscosity data

In der Einleitung werden die wichtigsten bisherigen Arbeiten uber die Fehlerfunktion mit komplexem Argument kurz besprochen. Die der vorliegenden Untersuchung unterworfene FunktionK(z) ist in Gleichung (1) definiert. Mit Hilfe der Laplace-Transformation und ihrer Umkehrformel wird gezeigt, wie sich die zwei Identitaten in Gleichung (3) behandeln lassen, so dass sowohl der Real-als auch der Imaginarteil der FunktionK(z) sich in zwei Teile aufspalten lasst, was aus den Gleichungen (9) und (9a) hervorgeht. Der erste Teil kann durch elementare Funktionen ausgedruckt werden, wahrend der zweite Teil sich durch zwei Integrale darstellen lasst. Fur die praktische Anwendung der angegebenen Ausdrucke sind in den Gleichungen (12), (12a) und (14a), (14b) die Ausdrucke in kartesischen bzw. polaren Koordinaten umgeschrieben worden. Der Vorteil der angegebenen Aufspaltung liegt darin, dass die in den Ausdrucken auftretenden Integrale monoton abnehmende Funktionen der unabhangigen Veranderlichen (x, y) darstellen und sich deswegen leicht numerisch ausrechnen lassen. Der Schwingungsanteil der FunktionK(z) ist ausschliesslich durch elementare Funktionen ausgedruckt. Im Appendix ist der Rechnungsvorgang, der zu den angegebenen Ausdrucken fuhrt, naher umschrieben.

On the error function of a complex argument

The paper reports the results of new measurements of the thermal conductivity of binary mixtures of helium, neon and argon with carbon monoxide at 27.5°C and in the pressure range 0.7–12 MPa. The viscosity of these mixtures had been measured previously. The availability of their interaction viscosity allows us to calculate the contribution of the internal degrees of freedom. The Monchick-Pereira-Mason equation provides a reasonable, but far from perfect, basis for a correlation. Even though the low-density viscosity of the present mixtures was essentially the same as the corresponding mixtures with nitrogen, the thermal conductivity is different, pointing to a significant contribution from the rotational degrees of freedom. A comparison between a calculation of the density effect based on a modification of the Thorne-Enskog theory due to Mason et al. shows the same reasonable agreement (of order 2%) as that ascertained in earlier measurements on other mixtures.

Thermal conductivity of three noble gases with carbon monoxide

The paper reviews the author's experience gained by his research on viscosity and thermal conductivity. The paper begins with a general discussion of the principles which must govern an experimenter who wishes to organize precise and accurate measurements of a transport property of a fluid. Emphasis is placed on the need to maintain a state close to equilibrium, to secure hydrodynamic stability, to formulate a faithful mathematical model of the process and to secure a high degree of resolution in the apparatus. The paper then proceeds to establish the principles which govern the measurement of viscosity in an oscillating-body instrument and briefly describes three such apparatus from the author's experience and one constructed in Trondheim by Torklep and Oye. The section on thermal conductivity concentrates on the author's hot-wire, transient instrument, and discusses the principle of its operation and its potential for use in liquids. The last section describes the contribution that the creation of a large body of accurate data on viscosity and thermal conductivity has made to the development of a completely reliable method of calculating these quantities for low-density monatomic gases and their multicomponent mixtures. This development is recounted here to serve as a possible model for the creation of a similar schema for the calculation of the transport properties of solutions.

Joseph Kestin

Papers

Diffusion Coefficient of Seven Binary Gaseous Mixtures

On the correlation of experimental viscosity data

On the error function of a complex argument

Thermal conductivity of three noble gases with carbon monoxide

Experimental determination of the viscosity and thermal conductivity of fluids